In my newest video, I give you an overview of dark matter, that mysterious stuff that makes up some 90 percent of the universe’s mass. During the last few decades, astronomers have gained convincing evidence that stars, gas, and dust aren’t all there is to the universe. Most of it is “dark” — both dark matter and dark energy. This video focuses on dark matter, and it’s the second video in a series called “Cosmology 101.”

Also check out the video about the Big Bang.

Editor’s note: “Cosmology 101: Dark Matter” is available to registered members of Astronomy.com. Registration is free, so sign up today to watch this video and enjoy other great benefits.